Cardiac Cycle Flashcards
at what phase is the heart relaxed and filling with blood?
diastole
what event marks the beginning of diastole?
AV opens
what are the 3 stages of diastole called, in order?
(after isovolumic relaxation)
1. rapid inflow
2. diastasis
3. atrial systole
what occurs during rapid inflow?
- AV valve open: ventricle is filled with blood from atria
- atrial volume & pressure drop
- ventricular volume & pressure increase
what occurs during diastasis?
(reduced filling)
AV valves still open: ventricular volume & pressure slowly increase
what occurs during atrial systole?
- atria contract (a-wave) -> push last 20% blood into ventricle
- increased ventricular pressure closes AV valve (S1)
what event marks the end of diastole?
AV valve closes
what must happen in order for the aortic valve to open?
overcome diastolic pressure
what phase occurs after the AV valve closes?
isovolumic contraction
what occurs during isovolumic contraction?
- atria relax (c-wave)
- ventricle contracts
- ventricular volume constant (no blood ejected)
- ventricular pressure increases
what event marks the end of isovolumic contraction?
aortic valve opens
what occurs during the ejection stage of systole?
- aortic valve is open
- ventricle contracts -> blood ejected from heart (ventricular volume decreases)
what event marks the end of systole?
aortic valve closes
what occurs when the aortic valve closes?
isovolumic relaxation
what occurs during isovolumic relaxation?
- aortic valve closes (S2)
- AV valve still closed = no change in ventricular volume
- ventricular pressure decreases
- slow flow of blood into atria (v-wave)
what marks the end of isovolumic relaxation?
atrial pressure > ventricular pressure = AV valve opens
in the atrial pressure curve, what does the a-wave represent and when does it occur?
- atrial contraction
- diastole: atrial systole
in the atrial pressure curve, what does the c-wave represent and when does it occur?
- ventricular contraction: AV valve bulges as ventricular P increases
- isovolumic contraction
in the atrial pressure curve, what does the v-wave represent and when does it occur?
- slow flow of blood into atria while AV valve closed
- isovolumic relaxation
why is atrial pressure always close to 0?
atria is a vein
what does the first heart sound (S1) represent?
AV valve closing (end of diastole)
what does the second heart sound (S2) represent?
aortic valve closing (end of systole)
what causes a potential third heart sound?
rapid filling of ventricles
what causes flaccid contraction of the heart?
excess serum K+ or low Ca++
what causes spastic contraction of the heart?
excess serum Ca++
what does the P wave in an ECG represent?
atrial depolarization
what does the QRS complex in an ECG represent?
ventricular depolarization
what event is “covered up” by the QRS complex?
atrial repolarization
what does the T wave in an ECG represent?
ventricular repolarization
at what phase does the heart receive blood supply (epicardial flow)?
diastole
what cellular event occurs during the rising phase of cardiac action potential?
voltage-gated fast Na+ and slow Ca++ channels open (both in)
what cellular event occurs during the plateau phase of cardiac action potential?
Ca++ activated Ca++ release from SR via ryanodine receptor
what cellular event occurs during the falling phase of cardiac action potential?
K+ channels open (out)
what controls the RMP of cardiac muscle?
Na/K ATPase pump and Na/Ca antiporter
in which phase of the ventricular muscle action potential is K+ permeability the highest?
3 (falling phase)
(K+ permeability of ventricle greatly increases, causing more negative membrane potential)
the AV valve is also known as the ____ valve
mitral
